<?php

HTMLPurifier_ConfigSchema::define(
	'Core', 'Encoding', 'utf-8', 'istring', 
	'If for some reason you are unable to convert all webpages to UTF-8, '. 
	'you can use this directive as a stop-gap compatibility change to '. 
	'let HTML Purifier deal with non UTF-8 input.  This technique has '. 
	'notable deficiencies: absolutely no characters outside of the selected '. 
	'character encoding will be preserved, not even the ones that have '. 
	'been ampersand escaped (this is due to a UTF-8 specific <em>feature</em> '.
	'that automatically resolves all entities), making it pretty useless '.
	'for anything except the most I18N-blind applications, although '.
	'%Core.EscapeNonASCIICharacters offers fixes this trouble with '.
	'another tradeoff. This directive '.
	'only accepts ISO-8859-1 if iconv is not enabled.'
);

HTMLPurifier_ConfigSchema::define(
	'Core', 'EscapeNonASCIICharacters', false, 'bool',
	'This directive overcomes a deficiency in %Core.Encoding by blindly '.
	'converting all non-ASCII characters into decimal numeric entities before '.
	'converting it to its native encoding. This means that even '.
	'characters that can be expressed in the non-UTF-8 encoding will '.
	'be entity-ized, which can be a real downer for encodings like Big5. '.
	'It also assumes that the ASCII repetoire is available, although '.
	'this is the case for almost all encodings. Anyway, use UTF-8! This '.
	'directive has been available since 1.4.0.'
);

if ( !function_exists('iconv') ) {
	// only encodings with native PHP support
	HTMLPurifier_ConfigSchema::defineAllowedValues(
		'Core', 'Encoding', array(
			'utf-8',
			'iso-8859-1'
		)
	);
	HTMLPurifier_ConfigSchema::defineValueAliases(
		'Core', 'Encoding', array(
			'iso8859-1' => 'iso-8859-1'
		)
	);
}

HTMLPurifier_ConfigSchema::define(
	'Test', 'ForceNoIconv', false, 'bool', 
	'When set to true, HTMLPurifier_Encoder will act as if iconv does not '.
	'exist and use only pure PHP implementations.'
);

/**
 * A UTF-8 specific character encoder that handles cleaning and transforming.
 * @note All functions in this class should be static.
 */
class HTMLPurifier_Encoder
{
	
	/**
	 * Constructor throws fatal error if you attempt to instantiate class
	 */
	function HTMLPurifier_Encoder() {
		trigger_error('Cannot instantiate encoder, call methods statically', E_USER_ERROR);
	}
	
	/**
	 * Error-handler that mutes errors, alternative to shut-up operator.
	 */
	function muteErrorHandler() {}
	
	/**
	/**
	 * Cleans a UTF-8 string for well-formedness and SGML validity
	 * 
	 * It will parse according to UTF-8 and return a valid UTF8 string, with
	 * non-SGML codepoints excluded.
	 * 
	 * @static
	 * @note Just for reference, the non-SGML code points are 0 to 31 and
	 *	   127 to 159, inclusive.  However, we allow code points 9, 10
	 *	   and 13, which are the tab, line feed and carriage return
	 *	   respectively. 128 and above the code points map to multibyte
	 *	   UTF-8 representations.
	 * 
	 * @note Fallback code adapted from utf8ToUnicode by Henri Sivonen and
	 *	   hsivonen@iki.fi at <http://iki.fi/hsivonen/php-utf8/> under the
	 *	   LGPL license.  Notes on what changed are inside, but in general,
	 *	   the original code transformed UTF-8 text into an array of integer
	 *	   Unicode codepoints. Understandably, transforming that back to
	 *	   a string would be somewhat expensive, so the function was modded to
	 *	   directly operate on the string.  However, this discourages code
	 *	   reuse, and the logic enumerated here would be useful for any
	 *	   function that needs to be able to understand UTF-8 characters.
	 *	   As of right now, only smart lossless character encoding converters
	 *	   would need that, and I'm probably not going to implement them.
	 *	   Once again, PHP 6 should solve all our problems.
	 */
	function cleanUTF8($str, $force_php = false) {
		
		// UTF-8 validity is checked since PHP 4.3.5
		// This is an optimization: if the string is already valid UTF-8, no
		// need to do PHP stuff. 99% of the time, this will be the case.
		// The regexp matches the XML char production, as well as well as excluding
		// non-SGML codepoints U+007F to U+009F
		if (preg_match('/^[\x{9}\x{A}\x{D}\x{20}-\x{7E}\x{A0}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]*$/Du', $str)) {
			return $str;
		}
		
		$mState = 0; // cached expected number of octets after the current octet
					 // until the beginning of the next UTF8 character sequence
		$mUcs4  = 0; // cached Unicode character
		$mBytes = 1; // cached expected number of octets in the current sequence
		
		// original code involved an $out that was an array of Unicode
		// codepoints.  Instead of having to convert back into UTF-8, we've
		// decided to directly append valid UTF-8 characters onto a string
		// $out once they're done.  $char accumulates raw bytes, while $mUcs4
		// turns into the Unicode code point, so there's some redundancy.
		
		$out = '';
		$char = '';
		
		$len = strlen($str);
		for($i = 0; $i < $len; $i++) {
			$in = ord($str{$i});
			$char .= $str[$i]; // append byte to char
			if (0 == $mState) {
				// When mState is zero we expect either a US-ASCII character 
				// or a multi-octet sequence.
				if (0 == (0x80 & ($in))) {
					// US-ASCII, pass straight through.
					if (($in <= 31 || $in == 127) && 
						!($in == 9 || $in == 13 || $in == 10) // save \r\t\n
					) {
						// control characters, remove
					} else {
						$out .= $char;
					}
					// reset
					$char = '';
					$mBytes = 1;
				} elseif (0xC0 == (0xE0 & ($in))) {
					// First octet of 2 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x1F) << 6;
					$mState = 1;
					$mBytes = 2;
				} elseif (0xE0 == (0xF0 & ($in))) {
					// First octet of 3 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x0F) << 12;
					$mState = 2;
					$mBytes = 3;
				} elseif (0xF0 == (0xF8 & ($in))) {
					// First octet of 4 octet sequence
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x07) << 18;
					$mState = 3;
					$mBytes = 4;
				} elseif (0xF8 == (0xFC & ($in))) {
					// First octet of 5 octet sequence.
					// 
					// This is illegal because the encoded codepoint must be 
					// either:
					// (a) not the shortest form or
					// (b) outside the Unicode range of 0-0x10FFFF.
					// Rather than trying to resynchronize, we will carry on 
					// until the end of the sequence and let the later error
					// handling code catch it.
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 0x03) << 24;
					$mState = 4;
					$mBytes = 5;
				} elseif (0xFC == (0xFE & ($in))) {
					// First octet of 6 octet sequence, see comments for 5
					// octet sequence.
					$mUcs4 = ($in);
					$mUcs4 = ($mUcs4 & 1) << 30;
					$mState = 5;
					$mBytes = 6;
				} else {
					// Current octet is neither in the US-ASCII range nor a 
					// legal first octet of a multi-octet sequence.
					$mState = 0;
					$mUcs4  = 0;
					$mBytes = 1;
					$char = '';
				}
			} else {
				// When mState is non-zero, we expect a continuation of the
				// multi-octet sequence
				if (0x80 == (0xC0 & ($in))) {
					// Legal continuation.
					$shift = ($mState - 1) * 6;
					$tmp = $in;
					$tmp = ($tmp & 0x0000003F) << $shift;
					$mUcs4 |= $tmp;
					
					if (0 == --$mState) {
						// End of the multi-octet sequence. mUcs4 now contains
						// the final Unicode codepoint to be output
						
						// Check for illegal sequences and codepoints.
						
						// From Unicode 3.1, non-shortest form is illegal
						if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
							((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
							((4 == $mBytes) && ($mUcs4 < 0x10000)) ||
							(4 < $mBytes) ||
							// From Unicode 3.2, surrogate characters = illegal
							(($mUcs4 & 0xFFFFF800) == 0xD800) ||
							// Codepoints outside the Unicode range are illegal
							($mUcs4 > 0x10FFFF)
						) {
							
						} elseif (0xFEFF != $mUcs4 && // omit BOM
							// check for valid Char unicode codepoints
							(
								0x9 == $mUcs4 ||
								0xA == $mUcs4 ||
								0xD == $mUcs4 ||
								(0x20 <= $mUcs4 && 0x7E >= $mUcs4) ||
								// 7F-9F is not strictly prohibited by XML,
								// but it is non-SGML, and thus we don't allow it
								(0xA0 <= $mUcs4 && 0xD7FF >= $mUcs4) ||
								(0x10000 <= $mUcs4 && 0x10FFFF >= $mUcs4)
							)
						) {
							$out .= $char;
						}
						// initialize UTF8 cache (reset)
						$mState = 0;
						$mUcs4  = 0;
						$mBytes = 1;
						$char = '';
					}
				} else {
					// ((0xC0 & (*in) != 0x80) && (mState != 0))
					// Incomplete multi-octet sequence.
					// used to result in complete fail, but we'll reset
					$mState = 0;
					$mUcs4  = 0;
					$mBytes = 1;
					$char ='';
				}
			}
		}
		return $out;
	}
	
	/**
	 * Translates a Unicode codepoint into its corresponding UTF-8 character.
	 * @static
	 * @note Based on Feyd's function at
	 *	   <http://forums.devnetwork.net/viewtopic.php?p=191404#191404>,
	 *	   which is in public domain.
	 * @note While we're going to do code point parsing anyway, a good
	 *	   optimization would be to refuse to translate code points that
	 *	   are non-SGML characters.  However, this could lead to duplication.
	 * @note This is very similar to the unichr function in
	 *	   maintenance/generate-entity-file.php (although this is superior,
	 *	   due to its sanity checks).
	 */
	
	// +----------+----------+----------+----------+
	// | 33222222 | 22221111 | 111111   |		  |
	// | 10987654 | 32109876 | 54321098 | 76543210 | bit
	// +----------+----------+----------+----------+
	// |		  |		  |		  | 0xxxxxxx | 1 byte 0x00000000..0x0000007F
	// |		  |		  | 110yyyyy | 10xxxxxx | 2 byte 0x00000080..0x000007FF
	// |		  | 1110zzzz | 10yyyyyy | 10xxxxxx | 3 byte 0x00000800..0x0000FFFF
	// | 11110www | 10wwzzzz | 10yyyyyy | 10xxxxxx | 4 byte 0x00010000..0x0010FFFF
	// +----------+----------+----------+----------+
	// | 00000000 | 00011111 | 11111111 | 11111111 | Theoretical upper limit of legal scalars: 2097151 (0x001FFFFF)
	// | 00000000 | 00010000 | 11111111 | 11111111 | Defined upper limit of legal scalar codes
	// +----------+----------+----------+----------+ 
	
	function unichr($code) {
		if($code > 1114111 or $code < 0 or
		  ($code >= 55296 and $code <= 57343) ) {
			// bits are set outside the "valid" range as defined
			// by UNICODE 4.1.0 
			return '';
		}
		
		$x = $y = $z = $w = 0; 
		if ($code < 128) {
			// regular ASCII character
			$x = $code;
		} else {
			// set up bits for UTF-8
			$x = ($code & 63) | 128;
			if ($code < 2048) {
				$y = (($code & 2047) >> 6) | 192;
			} else {
				$y = (($code & 4032) >> 6) | 128;
				if($code < 65536) {
					$z = (($code >> 12) & 15) | 224;
				} else {
					$z = (($code >> 12) & 63) | 128;
					$w = (($code >> 18) & 7)  | 240;
				}
			} 
		}
		// set up the actual character
		$ret = '';
		if($w) $ret .= chr($w);
		if($z) $ret .= chr($z);
		if($y) $ret .= chr($y);
		$ret .= chr($x); 
		
		return $ret;
	}
	
	/**
	 * Converts a string to UTF-8 based on configuration.
	 * @static
	 */
	function convertToUTF8($str, $config, &$context) {
		$encoding = $config->get('Core', 'Encoding');
		if ($encoding === 'utf-8') return $str;
		static $iconv = null;
		if ($iconv === null) $iconv = function_exists('iconv');
		set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
		if ($iconv && !$config->get('Test', 'ForceNoIconv')) {
			$str = iconv($encoding, 'utf-8//IGNORE', $str);
			// If the string is bjorked by Shift_JIS or a similar encoding
			// that doesn't support all of ASCII, convert the naughty
			// characters to their true byte-wise ASCII/UTF-8 equivalents.
			$str = strtr($str, HTMLPurifier_Encoder::testEncodingSupportsASCII($encoding));
			restore_error_handler();
			return $str;
		} elseif ($encoding === 'iso-8859-1') {
			$str = utf8_encode($str);
			restore_error_handler();
			return $str;
		}
		trigger_error('Encoding not supported', E_USER_ERROR);
	}
	
	/**
	 * Converts a string from UTF-8 based on configuration.
	 * @static
	 * @note Currently, this is a lossy conversion, with unexpressable
	 *	   characters being omitted.
	 */
	function convertFromUTF8($str, $config, &$context) {
		$encoding = $config->get('Core', 'Encoding');
		if ($encoding === 'utf-8') return $str;
		static $iconv = null;
		if ($iconv === null) $iconv = function_exists('iconv');
		if ($escape = $config->get('Core', 'EscapeNonASCIICharacters')) {
			$str = HTMLPurifier_Encoder::convertToASCIIDumbLossless($str);
		}
		set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
		if ($iconv && !$config->get('Test', 'ForceNoIconv')) {
			// Undo our previous fix in convertToUTF8, otherwise iconv will barf
			$ascii_fix = HTMLPurifier_Encoder::testEncodingSupportsASCII($encoding);
			if (!$escape && !empty($ascii_fix)) {
				$clear_fix = array();
				foreach ($ascii_fix as $utf8 => $native) $clear_fix[$utf8] = '';
				$str = strtr($str, $clear_fix);
			}
			$str = strtr($str, array_flip($ascii_fix));
			// Normal stuff
			$str = iconv('utf-8', $encoding . '//IGNORE', $str);
			restore_error_handler();
			return $str;
		} elseif ($encoding === 'iso-8859-1') {
			$str = utf8_decode($str);
			restore_error_handler();
			return $str;
		}
		trigger_error('Encoding not supported', E_USER_ERROR);
	}
	
	/**
	 * Lossless (character-wise) conversion of HTML to ASCII
	 * @static
	 * @param $str UTF-8 string to be converted to ASCII
	 * @returns ASCII encoded string with non-ASCII character entity-ized
	 * @warning Adapted from MediaWiki, claiming fair use: this is a common
	 *	   algorithm. If you disagree with this license fudgery,
	 *	   implement it yourself.
	 * @note Uses decimal numeric entities since they are best supported.
	 * @note This is a DUMB function: it has no concept of keeping
	 *	   character entities that the projected character encoding
	 *	   can allow. We could possibly implement a smart version
	 *	   but that would require it to also know which Unicode
	 *	   codepoints the charset supported (not an easy task).
	 * @note Sort of with cleanUTF8() but it assumes that $str is
	 *	   well-formed UTF-8
	 */
	function convertToASCIIDumbLossless($str) {
		$bytesleft = 0;
		$result = '';
		$working = 0;
		$len = strlen($str);
		for( $i = 0; $i < $len; $i++ ) {
			$bytevalue = ord( $str[$i] );
			if( $bytevalue <= 0x7F ) { //0xxx xxxx
				$result .= chr( $bytevalue );
				$bytesleft = 0;
			} elseif( $bytevalue <= 0xBF ) { //10xx xxxx
				$working = $working << 6;
				$working += ($bytevalue & 0x3F);
				$bytesleft--;
				if( $bytesleft <= 0 ) {
					$result .= "&#" . $working . ";";
				}
			} elseif( $bytevalue <= 0xDF ) { //110x xxxx
				$working = $bytevalue & 0x1F;
				$bytesleft = 1;
			} elseif( $bytevalue <= 0xEF ) { //1110 xxxx
				$working = $bytevalue & 0x0F;
				$bytesleft = 2;
			} else { //1111 0xxx
				$working = $bytevalue & 0x07;
				$bytesleft = 3;
			}
		}
		return $result;
	}
	
	/**
	 * This expensive function tests whether or not a given character
	 * encoding supports ASCII. 7/8-bit encodings like Shift_JIS will
	 * fail this test, and require special processing. Variable width
	 * encodings shouldn't ever fail.
	 * 
	 * @param string $encoding Encoding name to test, as per iconv format
	 * @param bool $bypass Whether or not to bypass the precompiled arrays.
	 * @return Array of UTF-8 characters to their corresponding ASCII,
	 *	  which can be used to "undo" any overzealous iconv action.
	 */
	function testEncodingSupportsASCII($encoding, $bypass = false) {
		static $encodings = array();
		if (!$bypass) {
			if (isset($encodings[$encoding])) return $encodings[$encoding];
			$lenc = strtolower($encoding);
			switch ($lenc) {
				case 'shift_jis':
					return array("\xC2\xA5" => '\\', "\xE2\x80\xBE" => '~');
				case 'johab':
					return array("\xE2\x82\xA9" => '\\');
			}
			if (strpos($lenc, 'iso-8859-') === 0) return array();
		}
		$ret = array();
		set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
		if (iconv('UTF-8', $encoding, 'a') === false) return false;
		for ($i = 0x20; $i <= 0x7E; $i++) { // all printable ASCII chars
			$c = chr($i);
			if (iconv('UTF-8', "$encoding//IGNORE", $c) === '') {
				// Reverse engineer: what's the UTF-8 equiv of this byte
				// sequence? This assumes that there's no variable width
				// encoding that doesn't support ASCII.
				$ret[iconv($encoding, 'UTF-8//IGNORE', $c)] = $c;
			}
		}
		restore_error_handler();
		$encodings[$encoding] = $ret;
		return $ret;
	}
	
	
}

